Glass fiber mats



Dec. 5, 1967 G. 1.. SQUIRE ETAL 3,356,561

GLASS FIBER MATS Filed Nov. '7, 1962 INVENTORS' 660/?65 1 .5 Q ume United States Patent 3,356,561 GLASS FIBER MATS George L. Squire, Ridley Park, Pa., and John M. Ward, Wilmington, Del., wsignors to Haveg Industries, Inc., a wholly owned subsidiary of Hercules Powder Company, New Castle, Del., a corporation of Delaware Filed Nov. 7, 1962, Ser. No. 236,041 4 Claims. (Cl. 161-80) This invention relates to the preparation of glass fiber mats.

When glass fiber mats from material woven from yarns are needled with strands of chopped glass fibers to reinforce the same, it has been found that the product is of poor quality because of the brittleness of the base fabric. This is particularly true if the glass mat is subsequently leached with acid to form high silica content mats since the acid treatment increases the brittleness. The tensile strength of the scrim fabric to which the chopped strands had been needled is greatly decreased by the needling process, and the fabric virtually falls apart during the acid leaching. This is true even with the stronger fabrics woven from glass yarns. The needling process appears to destroy the integrity of the individual yarns.

Methods employed for strengthening other textile materials are often ineffective with glass fibers due to the brittleness of the fibers.

It is an object of the present invention to prepare high silica glass fiber mats of increased tensile strength.

Another object is to prepare acid leached glass fiber mats having a high silica con-tent, which mats do not fall apart in the acid leaching step.

A further object is to prepare high silica fiber mats having improved physical properties.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

It has now been found that these objects can be attained by inserting glass fibers on both sides of a woven roving glass cloth. It is important that the glass cloth be made of roving rather than yarn.

It has been observed that the rovings have large numbers of unidirectional filaments which are not destroyed by the subsequent needling operation and acid leaching. In contrast, as previously stated, when yarns are employed to prepare woven glass fabrics, the integrity of the individual yarns is destroyed by the needling step.

The glass fibers in the form of chopped glass strands are needled into the roving glass cloth base whereby loose fibers as such or in the form of tufts are inserted into the fabric base. Preferably, the glass fibers are garnetted or napped, as well as needled to give the appearance of fleece.

The chopped glass strands can be made of twisted rovings or yarns. Usually, they are one-half inch in length but they can be of any length. There is no problem of destroying the integrity of the individual yarns which are needled into the fabric and consequently, as indicated supra, yarns as well as rovings can be employed whereas it is essential that only rovings be employed to make the Woven fabric or scrim.

After the relatively heavy woven roving glass cloth is needled (or needled and garnetted), the product is acid 3,356,561 Patented Dec. 5, 1967 leached, e.g., as shown in Moore Patent 2,995,803 or Parker Patents 2,624,658 and 2,686,954.

The invention will be understood best with reference to the drawing wherein:

The single figure is a perspective view partially broken away showing a glass cloth according to the invention.

Referring more specifically to the drawing, there is provided a glass cloth 2 comprising a woven glass roving core 4 which is needled and garnetted on both sides as shown at 6 and 8 whereby tufts of fleeced loose fibers are inserted into the fabric core 4 to give a strong product. This material is then acid leached to a sodium car bonate soluble silica content of at least 70%, and preterably between and The sodium carbonate soluble silica content can be as high as 99%. The total silica content is always at least as high as the sodium carbonate soluble silica and preferably is 95% or above, e.g., 99%.

The acid leaching is preferably carried out with aqueous hydrochloric acid at temperatures of 230 F. The hydrochloric acid can be of 5 to 30% concentration, preferably 10 to 15%.

In place of aqueous hydrochloric acid there can be employed other acids such as nitric acid, trichloroacetic acid, sulfuric acid, acetic acid, hydrobromic acid, etc.

After the acid extraction, the glass fibers can be heated to 1700 to 2350 F. to form a dimensionally stable fabric, although this latter treatment is not required for many uses.

In a specific example there was employed a woven roving glass cloth made from 210 roving of type B electrical grade fibers (silica content 54%). The cloth had a weight of 46 pounds per cubic foot, and there was approximately the same amount of fibers in the warp and filler directions. This cloth which was between A and inch thick was then needled and garnetted on both sides with chopped strands of yarns made of type B glass fibers. The product was then extracted with 13% hydrochloric acid at F. until the sodium carbonate soluble silica content was 92.5% and the total silica was 98%.

The product was heated to 1900 F. until the fabric was dimensionally stable.

Glass cloth having a weight of 15 to 17 pounds per cubic foot can be employed.

The acid etched, needled and garnetted woven roving glass cloth of the present invention is useful as a reinforcement for impregnation with synthetic resins where a heavier section is desired. It is also useful as backup for electric welding blankets, gaskets for high temperature applications, furnace liners and seals, gas and liquid filters, catalyst supports, automobile mufiler packing and high temperature insulation.

The term roving as employed in the present specification and claims is used in its art-accepted sense to mean slightly twisted fibers which are intermediate stage between slivers and yarns, see Man-Made Textile Encyclopedia, published by Textile Book Publishers, Inc., New York, NY. (1959).

The term needled on both sides as used in the claims signifies that the fibers inserted by the needle extend through the top and bottom of the cloth core.

We claim:

1. As a new product woven acid extracted glass cloth made of type E fibers having loose glass fibers independent of and extending into and through both sides of the cloth, said etched glass having a sodium carbonate soluble silica content of at least 70%.

2. A product according to claim 1 wherein the sodium carbonate soluble silica content is between 90 and 95% 3 4 3. A product according to claim 1 wherein the loose 2,991,536 7/1961 Moler 2872.2, fibers are in the form of fleece. 2,995,803 8/ 1961 Moore 65-24 4. A product according to claim 1 which has been 3,044,146 7/1962 Thomas et a1. 28-78 rendered dimensionally stable by heating to a temperature between 1700 and 2350 F. 5 FOREIGN PATENTS 87 ,0 24 10 1 61 {B 't References Cited 9 9 Grea r1 am UNITED STATES PATENTS EARL M. BERGERT, Primary Examiner.

1,742,338 1/ 1930 Bettison 2872.2 W. E HOAG, Assistant Examiner. 2,794,238 6/1957 Dildilian et a1. 28-79 10 

1. AS A NEW PRODUCT WOVEN ACID EXTRACTED GLASS CLOTH MADE OF TYPE E FIBERS HAVING LOOSE GLASS FIBERS INDEPENDENT OF AND EXTENDING INTO AND THROUGH BOTH SIDES OF THE CLOTH, 